In the course of a three-year research project comparing social media and political participation across the European Union, we collected data on representative samples of internet users from Germany, Italy and the UK. Online users were surveyed just after the May 2014 European elections. The three countries have been selected as they differ not only in terms of institutional features but also in terms of the character of their media systems: ‘liberal’ in the UK, ‘democratic-corporatist’ in Germany and ‘polarized pluralist’ in Italy. Although previous studies have not put into direct relationship media systems with participatory patterns, we hypothesized that different types of media ecologies may generate peculiar incentives for non-institutional participation. Taking such differences into account, our paper sheds light on the linkage between digital media and unconventional participation across the three countries. Our hypothesis is that distinct news diets and different social media platforms may influence non-institutional participation in specific ways that reflect varying contextual characteristics. We assess the role of different news diets on unconventional participation, distinguishing our respondents according to their main sources of information (occasional, traditional univores, digital univores and omnivores). We then consider the association between the use of different social media (i.e. Facebook and Twitter) and non-institutional participation. Finally, we take into account the indirect effect of national contexts by running interaction models. Our findings show that news diets and social media use matter in the three countries, but that substantial differences are hard to find across them.